Non-invasive method of determining diastolic intracranial pressure

Abstract

A method is presented for determining diastolic intracranial pressure (ICP) in a patient. A first change in the length of a path across the skull of the patient caused by a known change in ICP is measured and used to determine an elasticity constant for the patient. Next, a second change in the length of the path across the patient's skull occurring between systolic and diastolic portions of the patient's heartbeat is measured. The patient's diastolic ICP is a function of the elasticity constant and the second change.

What is claimed as new and desired to be secured by Letters Patent of the United States is:  
     
       1. A method of determining diastolic intracranial pressure (ICP) in a patient, comprising the steps of: 
       measuring a first change in the length of a path across the skull of the patient caused by a known change in ICP in the patient, wherein said first change in the length of said path relative to said known change in ICP is indicative of an elasticity constant for the patient; and  
       measuring a second change in the length of said path occurring between systolic and diastolic portions of a heartbeat of the patient, wherein a diastolic ICP is a function of said elasticity constant and said second change in the length of said path.  
     
     
       2. A method according to  claim 1  wherein each of said steps of measuring comprises the steps of: 
       coupling an acoustic signal to a first location on the patient's skin adjacent the skull of the patient;  
       detecting said acoustic signal at a second location on the patient's skin adjacent the skull of the patient; and  
       measuring a phase difference between said acoustic signal so-coupled at said first location and said acoustic signal so-detected at said second location, wherein said phase difference is indicative of one of said first change and said second change.  
     
     
       3. A method according to  claim 2  further comprising the step of applying pressure to the patient's skin at each of said first location and said second location prior to said steps of coupling and detecting, wherein pulsatile blood perfusion at said first location and said second location is reduced. 
     
     
       4. A method according to  claim 2  wherein said first location and said second location are approximately diametrically-opposed to one another on either side of the skull of the patient. 
     
     
       5. A method according to  claim 2  wherein said first location and said second location are approximately the same location. 
     
     
       6. A method according to  claim 1  wherein said known change in ICP is induced by the step of manipulating the patient in a mechanical fashion. 
     
     
       7. A method according to  claim 1  wherein said known change in ICP is induced by the step of manipulating the patient in a chemical fashion. 
     
     
       8. A method of determining diastolic ICP in a patient, comprising the steps of: 
       measuring a first change Δl in the length of a path across the skull of the patient caused by a known change ΔICP in ICP in the patient, wherein ΔICP/Δl defines an elasticity constant K for the patient; and  
       measuring a second change Δx in the length of said path occurring between systolic and diastolic portions of a heartbeat of the patient, wherein a diastolic ICP is equal to A(KΔx) B , where A and B are constants derived from a data relationship between pulsatile variations in ICP and a mean diastolic ICP, wherein said data relationship is defined for a general human population.  
     
     
       9. A method according to  claim 8  wherein each of said steps of measuring comprises the steps of: 
       coupling an acoustic signal to a first location on the patient's skin adjacent the skull of the patient;  
       detecting said acoustic signal at a second location on the patient's skin adjacent the skull of the patient; and  
       measuring a phase difference between said acoustic signal so-coupled at said first location and said acoustic signal so-detected at said second location, wherein said phase difference is indicative of one of said first change and said second change.  
     
     
       10. A method according to  claim 9  further comprising the step of applying pressure to the patient's skin at each of said first location and said second location prior to said steps of coupling and detecting, wherein pulsatile blood perfusion at said first location and said second location is reduced. 
     
     
       11. A method according to  claim 9  wherein said first location and said second location are approximately diametrically-opposed to one another on either side of the skull of the patient. 
     
     
       12. A method according to  claim 9  wherein said first location and said second location are approximately the same location. 
     
     
       13. A method according to  claim 8  wherein said known change in ICP is induced by the step of manipulating the patient in a mechanical fashion. 
     
     
       14. A method according to  claim 8  wherein said known change in ICP is induced by the step of manipulating the patient in a chemical fashion. 
     
     
       15. A method of determining diastolic ICP in a patient, comprising the steps of: 
       coupling an acoustic signal to a first location on the patient's skin adjacent the skull of the patient;  
       detecting said acoustic signal at a second location on the patient's skin adjacent the skull of the patient;  
       inducing a known change in ICP in the patient;  
       measuring a first phase difference between said acoustic signal so-coupled at said first location and said acoustic signal so-detected at said second location, said first phase difference being caused by said known change in ICP, wherein said first phase difference is indicative of a first change in the length of a path across the skull of the patient, and wherein said first change in the length of said path relative to said known change in ICP is indicative of an elasticity constant for the patient;  
       repeating said steps of coupling and detecting; and  
       measuring, during said step of repeating, a second phase difference between said acoustic signal so-coupled at said first location and said acoustic signal so-detected at said second location, said second phase difference occurring between systolic and diastolic portions of a heartbeat of the patient, wherein said second phase difference is indicative of a second change in the length of said path occurring between said systolic and diastolic portions, wherein a diastolic ICP is a function of said elasticity constant and said second change in the length of said path.  
     
     
       16. A method according to  claim 15  further comprising the step of applying pressure to the patient's skin at each of said first location and said second location prior to said steps of coupling and detecting, wherein pulsatile blood perfusion at said first location and said second location is reduced. 
     
     
       17. A method according to  claim 15  wherein said first location and said second location are approximately diametrically-opposed to one another on either side of the skull of the patient. 
     
     
       18. A method according to  claim 15  wherein said first location and said second location are approximately the same location. 
     
     
       19. A method according to  claim 15  wherein said known change in ICP is induced by the step of manipulating the patient in a mechanical fashion. 
     
     
       20. A method according to  claim 15  wherein said known change in ICP is induced by the step of manipulating the patient in a chemical fashion.